Insufflation device with intelligent control of smoke evacuation

ABSTRACT

The present invention relates to an insufflator with integrated smoke evacuation. By virtue of a novel control method of the evacuation volumetric flow rate, the following advantages are achieved. First, a reduction of the pressure in the cavity due to the evacuation is prevented. An empirically determined safety factor is determined, which results in the evacuation volumetric flow rate not exceeding the maximum possible insufflation volumetric flow rate. Second, the exchange volumetric flow rate is limited. It is limited such that the sum of the currently calculated leakage and the evacuation volumetric flow rate does not exceed a defined value. Thus, stress on the patient due to unnecessarily high exchange volumetric flow rates and the associated cooling and drying processes is prevented.

The present invention relates to an insufflator with integrated smokeevacuation. A novel control method of the smoke evacuation enables tomaintain the pressure in the patient even when leakages occur, and tolimit the evacuation volumetric flow rate in case of high leakages.

BACKGROUND AND PRIOR ART

Insufflators offering the possibility of a simultaneous smoke evacuationare known from prior art (see, e.g., WO 2015/043570 A1). Thisinsufflator comprises a hose, through which a medical gas is fed into abody cavity (e.g., an abdomen). The gas generates a positive pressure,which expands the body cavity, in order that there is sufficient spacefor visual inspections or therapeutic interventions. Through a secondhose, the gas is evacuated again from the abdomen. In the case oftherapeutic interventions by means of electrical surgery or laser,obnoxious smoke gases may be formed that are discharged and filtered bythe insufflator via this second hose. The surgeon selects a desiredtarget evacuation volumetric flow rate. The evacuation pump is regulatedto the desired target evacuation volumetric flow rate. It is a problemwhen a larger leakage volumetric flow occurs or the resistance to flowof the insufflation line increases. In either case, the insufflator isnot capable of insufflating the additionally necessary amount of CO₂.The consequence is that the cavity partially or completely collapses. Inorder to reduce this effect, according to the state of the art, theevacuation volumetric flow rate is limited or reduced in suchsituations. One possibility of implementation is to detect whether themeasured pressure in the cavity differs from the desired target value,and then to reduce the maximum evacuation volumetric flow rate.

Most insufflators available on the market operate with a pulse-likemethod, in order to regulate the volumetric flow rate to be insufflated.Herein, insufflation phases alternate with so-called “measurementpauses”. In the measurement pauses, the volumetric flow is turned offfor a few hundred milli-seconds, so that the pressure in the hose andthe pressure in the cavity are balanced. Thereby, the insufflator canmeasure, by a pressure sensor in the insufflation line, for a short timethe pressure in the cavity. Through the length of the insufflationphases, then the mean insufflation volumetric flow rate is controlled.When high volumetric flow rates are required, long insufflation phasesare performed. In such a pulsed insufflation method, another possibilityof regulating the evacuation flow is to use the length of aninsufflation phase as a criterion for a decrease or an increase of theevacuation volumetric flow rate. When, for instance, the necessarylength of the insufflation phase exceeds a predefined value, the smokeevacuation is reduced.

In the practice, it has been found that these two methods for limitingthe evacuation volumetric flow rate have drawbacks. The most importantdrawback is that the pressure in the cavity must already have beenreduced, in order that the evacuation volumetric flow rate is adjusted.This means that, when opening leakages, undesired pressure drops willoccur, which can lead to delays in the surgery. An example is a largerleakage that occurs during the surgery.

Advanced insufflators are capable of generating insufflation volumetricflow rates of higher than 30 Ipm. Thereby, even high leakages can bebalanced, and simultaneously, a sufficient reserve for evacuation can beprovided. This has, however, the following drawback: Even with highleakages, wherein, for surgeons, in fact, no evacuation would berequired, the evacuation is not reduced. The evacuation continues withfull evacuation power and stresses the patient by an additional coolingand drying process of the tissue. In order to reduce this drawback, inU.S. Pat. No. 5,199,944, a method is proposed, which only starts thesmoke evacuation when smoke gases are generated. Further state of theart follows from the document US 2018/0133416 A1. In the present patentdocument, an alternative method is described.

The present invention relates to an insufflator for minimally invasivesurgery, including a) a pressure and flow rate-regulating unit equippedwith a proportional valve, a pressure sensor and a flow rate measurementdevice, b) a supply line with an optional filter and connection to afirst trocar, c) a second trocar with an evacuation hose and an optionalfilter, connected to an evacuation device with controllable evacuationpower, d) an optional flow rate measurement device in the evacuationline, e) an electronic or mechanical regulating unit, and f) a novelmethod for adjustment of the evacuation volumetric flow rate.

With small leakages, the insufflator is operated, as is described in thestate of the art (WO 2015/043570 A1). The gas connection (1) leads via aline (2) to the pressure and flow rate-regulating unit (3) of the supplyline (4). In the pressure and flow rate unit (3) is provided a pressuresensor, in order to monitor the pressure in the line. Furthermore, aflow rate-measurement device (5) is mounted for volumetric flow ratemeasurement behind the pressure and flow rate unit (3). Further, afilter for protection of the patient is provided (6). The supply line(7) terminates in a first trocar (8) that can fill the body cavity withgas. The insufflator further includes a second hose (10) serving as anevacuation hose. A second trocar (9) introduced into the body cavity (9)is connected by means of this evacuation hose (10) to the insufflator.The evacuation hose, too, comprises an optional filter (11) and leadsvia a line (13) to an evacuation pump (14). The evacuation power of theevacuation pump is controllable. Via a line (15), the smoke isdischarged from the insufflator (16).

The evacuation volumetric flow rate can be measured either through theoptional flow rate sensor (12) or can be determined by the power of theevacuation pump (14). Different from insufflators of prior art, theinsufflator according to the invention comprises a novel intelligentcontrol method of the evacuation volumetric flow rate.

The novel method for adjustment of the evacuation volumetric flow ratecomprises the following steps:

(a) Determination of the current maximum insufflation power: The maximuminsufflation volumetric flow rate is mainly dependent on the resistanceto flow of the used trocar-instrument combination and the maximumpressure.

This pressure is typically set to a value, which leads to a stillacceptable risk for the patient and must not further be increased. Inorder to determine the maximum possible insufflation volumetric flowrate, different methods can be used. For instance, an algorithm can beused, which determines the characteristic of the trocar instrument.Alternatively, mathematical models, such as the Kalman filter orLuenberger observer, can be used to determine the maximum insufflationpower.

(b) Determination of the current leakage volumetric flow rateq_(Leakage): The leakage, too, can be estimated by a mathematical model.Alternatively, the mean leakage can also approximately be calculated bya subtraction of the mean evacuation volumetric flow rate from the meaninsufflation volumetric flow rate.

(c) Calculation of the maximum possible evacuation volumetric flow rateq_(Evacuation,max): By subtraction of the determined leakage from themaximum insufflation flow rate and subsequent multiplication with asafety factor between 0 and 1, which defines, with which load theinsufflator ideally is stressed. The value is typically between 0.6 and0.9.

(d) Verification whether a maximum exchange flow is exceeded:

In order to prevent that a high evacuation volumetric flow rate remainsadjusted, even when in this situation leakages cause already a high gasexchange, the evacuation volumetric flow rate is additionally limited.For this purpose, a maximum exchange volumetric flow rateq_(Exchange,max) is defined. Typical values for q_(Exchange,max) arebetween 10 and 20 Ipm. The value either can be adjusted via a graphicalinterface or is fixedly configured in the insufflator or adjusted by thesoftware. The maximum evacuation volumetric flow rate q_(Exchange,max)is then limited such that the equationq_(Evacuation,max)+q_(Leakage)≤q_(Exchange,max) is satisfied. In otherwords: The sum of the maximum evacuation volumetric flow rate and theestimated leakage must not be larger than a defined value forq_(Exchange,max).

(d) If the evacuation volumetric flow rate adjusted by the surgeon islarger than the calculated maximum evacuation volumetric flow rateq_(Exchange,max), the target evacuation volumetric flow rate is limitedto the maximum allowed evacuation volumetric flow rateq_(Evacuation,max).

(e) The calculation is cyclically repeated (for instance every second),in order that the maximum allowed evacuation volumetric flow rate cancontinuously be adapted to changes in leakage or changes in thetrocar-instrument combination.

A calculation example for illustration:

(a) The characteristic of the trocar-instrument combination isdetermined as q_(Instrument) =0.2 Ipm/mmHg×p_(Hose) with the volumetricflow rate q_(Instrument) and the pressure in the hose p_(Hose). Thepressure for acceptable safety may be 100 mmHg. Then follows a maximumvolumetric flow rate of q_(max) =0.2 Ipm/mmHg×100 mmHg=20 Ipm.

(b) The leakage is estimated by an observer or another method to be 10Ipm.

(c) The safety factor is selected as 0.8. Then follows a maximumevacuation flow q_(Evacuation,max) =20 Ipm×0.8-10 Ipm=6 Ipm.

(d) When the surgeon has selected an evacuation volumetric flow rate offor instance 8 Ipm, this is reduced to the maximum evacuation volumetricflow rate q_(Evacuation,max) =6 Ipm, in order to prevent that thepressure is reduced too much by the selected evacuation.

(e) When the maximum exchange volumetric flow rate q_(Exchange,max) wasconfigured to be 18 Ipm, the conditionq_(Evacuation,max)+q_(Leakage)≤q_(Exchange,max) is satisfied. Thus,there is no further reduction of the evacuation volumetric flow rate bythe maximum exchange volumetric flow rate. When the maximum exchangevolumetric flow rate q_(Exchange,max) would have been configured to be12 Ipm, the evacuation volumetric flow rate would be reduced to 2 Ipm.

(f) The calculation is cyclically repeated, and when for instance themaximum insufflation power q_(max) is reduced, q_(Evacuation,max) isalso adjusted.

1.-4. (canceled)
 5. An insufflator for providing gas to a patient cavityduring minimally invasive surgery, comprising: a) a gas connectionadapted for receiving a gas supply and providing the gas supply to apressure and flow rate regulating unit equipped with a flow ratemeasuring unit, a proportional valve and a pressure sensor; b) a supplyline for receiving gas from the pressure and flow rate regulating unit,the supply line connected to a first trocar for providing pressurizedgas to the patient cavity; c) a second trocar connected to an exhaustline which is operatively connected to an evacuation device for removingflue gas from the patient cavity; d) a device for determining of theevacuation volumetric flow rate; and e) a controller operativelyconnected to the pressure and flow rate regulating unit and theevacuation device; wherein the controller controls the evacuation deviceso as to adjust the evacuation volumetric flow rate based at least inpart on a defined maximum exchange volumetric flow rate and a determinedleakage volumetric flow rate.
 6. The insufflator as recited in claim 5,wherein the insufflator further includes a second flow rate measuringunit operatively positioned in a flow path between the evacuation deviceand the second trocar for measuring the evacuation volumetric flow rate.7. The insufflator as recited in claim 5, further including unit fordetermining a power supplied to the evacuation device, wherein thedetermination of power is used to estimate the evacuation volumetricflow rate.
 8. The insufflator as recited in claim 5, wherein thepressure sensor is positioned within the pressure and flow rateregulating unit.
 9. A method for operating the insufflator of claim 5,comprising the steps of: a. determine a maximum possible insufflationvolumetric flow rate based on a flow resistance characteristic; b.determine a current leakage volumetric flow rate; c. multiply themaximum possible insufflation volumetric flow rate with a safety factorto determine a reduced maximum insufflation volumetric flow rate, d.determining a maximum allowed evacuation volumetric flow rate bysubtraction of the current leakage volumetric flow rate from the reducedmaximum insufflation volumetric flow rate; e. defining a maximumexchange volumetric flow rate; f. determine whether the maximum exchangeflow rate is exceeded based on the maximum evacuation volumetric flowrate and the current leakage volumetric flow rate; and g. limit andreduce the maximum evacuation volumetric flow rate if the maximumexchange flow rate is exceeded.
 10. The method according to claim 9,wherein the maximum possible insufflation volumetric flow rate isdetermined using a mathematical algorithm
 11. The method according toclaim 9, wherein the maximum possible insufflation volumetric flow rateis determined using a mathematical model.
 12. The method according toclaim 11, wherein the mathematical model is a Jalman filter.
 13. Themethod according to claim 11, wherein the mathematical model is aLuenberger observer.
 14. The method according to claim 9, the currentleakage volumetric flow rate is determined by an observer or mean valueformation.
 15. The method according to claim 9, wherein the safetyfactor used for determining the reduced maximum insufflation volumetricflow rate is about between 0.6 and 0.9.
 16. The method according toclaim 9, wherein the maximum exchange flow rate is between about 10 and20 Ipm.